Finding that the simple drying of skins would not properly prepare them for clothing, primeval man would naturally look for some means of treating them to conserve their original softness and pliability, and the nearest substances at hand would be animal fats and brains. It is almost safe to assume that this process was the first by which hides were preserved in a state differing from their original condition, the oxidation of the fatty matters naturally producing a partial tannage. The effect of smoke may also have been discovered in the earliest days of skin-curing, and it is reported that even now one or two tribes use smoke to preserve skins. The somewhat imperfect preservation of the hides by this method would lead to further experiments being made, which evidently resulted in the discovery of the tanning effect of leaves, twigs, and barks of trees when soaked in water. It may be that the preservative effect of alum was discovered even before the vegetable tanning process, for the original Japanese white leather was made simply by steeping the raw hides in certain rivers which contained a bed-rock of alum. This primitive process is even followed to-day in one or two places in Japan, but the leather is afterwards treated with oil to impart tensile strength and increased suppleness. Strictly speaking, these hides are not leather when finished, and they are quite unsuitable for boots; but, being the toughest material known in the leather trade, with the possible exception of raw hide, it is particularly suitable and chiefly used for brace ends, and occasionally for ladies' belts. It must not be inferred from reference to this process that the Japanese only use this earliest method of making leather; on the contrary, they are producing all classes of leather, and especially belting and sole, by modern European methods, and it may not be long before their competition with American and European productions becomes an accomplished fact.